1. Field of the Invention
This invention relates to the design, synthesis, and administration of immunoconjugate reagents for treating patients having diseases associated with the growth of new blood vessels (neovascularization) such as cancer, rheumatoid arthritis, the exudative form of macular degeneration, and atherosclerosis. The target for immunoconjugates of the invention is the transmembrane receptor tissue factor expressed by endothelial cells of the neovasculature. Tissue factor also is expressed by many types of tumor cells. Therefore, therapeutic methods of the invention are especially efficacious in immunotherapy against a broad range of solid tumors. The therapeutic reagent is an immunoconjugate composed of a targeting domain and an effector domain (FIG. 1). The targeting domain is a mutated form of factor VII that binds with high affinity and specificity to tissue factor, but does not initiate blood coagulation. The effector domain is the Fc region of an IgG1 immunoglobulin.
2. Background of the Invention
Pathologic angiogenesis, the induction of the growth of blood vessels from the vessels in surrounding tissue, is observed in a variety of diseases, typically triggered by the release of specific growth factors for vascular endothelial cells. Pathologic angiogenesis can result in neovascularination, enabling solid tumor growth and metastasis, causing visual malfunction in ocular disorders, promoting leukocyte extravasation in inflammatory disorders, and/or influencing the outcome of cardiovascular diseases such as atherosclerosis. Collectively, these are sometimes referred to as angiogenic diseases.
Since the survival and growth of a solid tumor depend critically on the development of a neovasculature, cancer is a paramount angiogenic disease (Folkman, J. (1995) N. Engl. J. Med. 333, 1757-1763). Many cancers progress in stages, beginning with proliferation of primary tumor cells, then penetration of tumor cells into the circulatory system, colonization at disseminated metastatic sites, and proliferation of the metastasized tumor cells which are responsible for most deaths from cancer (Vogelstein, B., and Kinzler, K. W. (1993) TIG 9, 141-143). Because cancer often remains undetected until the disease has reached the metastatic stage, cancer therapies that can eradicate the vascular infrastructure and metastatic tumor cells are particularly desirable.
Angiogenesis also plays a significant role in rheumatoid arthritis (Szekanez, Z., et al. (1998) J. Invest. Med. 46, 27-41). Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease that occurs worldwide in all ethnic groups and predominantly affects diarthrodial joints and frequently a variety of other organs. The RA synovial tissue is extensively neovascularized. In RA, inflammatory leukocytes emigrate into the synovium through the endothelial layer of blood vessels, resulting in synovial inflammation and, eventually, joint destruction.
Angiogenesis underlies the majority of eye diseases that result in catastrophic loss of vision (Friedlander, M., et al. (1996) Proc. Natl. Acad. Sci. USA 93, 9764-9769). The leading cause of blindness in individuals over the age of 55 is the exudative (“wet”) form of age-related macular degeneration (ARMD), and under the age of 55, proliferative diabetic retinopathy (PDR). While ARMD and PDR are prototypic diseases for choroidal and retinal neovascularization, respectively, other degenerative or inflammatory conditions can selectively cause angiogenesis of either vasculature (ibid.).
Therefore, one approach to the treatment of these disease states, and particularly of cancer, has been to compromise the function or growth of the neovasculature, primarily by inhibiting the growth of new blood vessels (Chaplin, D. J., and Dougherty, G. J., (1999) Br. J. Cancer, 80, 57-64). There are several advantages to vascular targeting. First, damage to blood vessels could stop blood flow and, applied to cancer, can trigger death of many dependent tumor cells. Second, the target cells are adjacent to the bloodstream, enhancing drug delivery. Third, treatment-resistant mutations are not likely to emerge in vascular endothelial cells.
A number of anti-angiogenic therapies have been suggested, including drug, antibody, and gene therapy-based approaches. These include metalloproteinase inhibitors, pentosan polysulphate and TNP-470, selective inhibitors of tyrosine kinase, and peptide inhibitors of angiostatin and endostatin (ibid., and reviews cited therein). These typically prevent angiogenesis at various stages of vessel formation, i.e., basement membrane degradation, endothelial cell migration, endothelial cell proliferation, and tube formation. It would be desirable to have improved therapies that target not only angiogenesis, but also the neovasculature already formed in angiogenic disease states.